What does DSL stand for?
Digital Subscriber Line. DSL is a modem technology that transforms ordinary phone lines (also known as "twisted copper pairs") into high-speed digital lines for ultra-fast Internet access. DSL also enables access to corporate networks for telecommuters, as well as exciting new interactive multimedia applications such as multiplayer gaming, video on demand and video catalogs.

What is xDSL?
xDSL is the name which has been coined for the family of digital subscriber line technologies ranging from ADSL to SDSL. The "x" represents a varible that can be replaced with either the "A" standing for ASYNCHRONUS or "S" standing for SYNCHRONUS. 2COOLWEB Services provides both.

How does xDSL work?
xDSL modems use digital coding techniques to squeeze up to 99% more capacity out of a phone line without interfering with your regular phone services. That means you could be simultaneously talking on the phone or sending a fax - while surfing the World Wide Web, since the DSL service operates off another separate phone circuit and does NOT need to tie-up your current voice and/or fax line. 

What is the market for xDSL?
xDSL enables two general types of applications -- interactive video and high speed data communications. Interactive video includes movies on demand, other video on demand such as delayed TV segments, video games, video catalogs, and video information retrieval. Data communications covers Internet access, telecommuting (remote LAN access), and specialized network access. The strength of xDSL compared to other high speed transmission alternatives (such as cable modems or Fiber To The Neighborhood (FTTN) lies in the number of existing telephone lines -- now approaching 750 million -- compared to new cabling which has reached comparatively few homes and almost no small businesses.

What will xDSL do to ISDN?
That all depends upon the telephone companies offering both services. The two services are not the same -- ISDN provides two voice channels or a 128 Kbps data channel while xDSL is predominantly a data pipe providing an asymmetrical bandwidth of up to 8 Mbps downstream and 1 Mbps upstream under good conditions. However, an xDSL access network will be an overlay network and therefore will not require the expensive and time-consuming switch upgrades that held ISDN back for so long. If xDSL service prices resemble ISDN service prices, then one would expect xDSL to be favored for Internet and video applications.

What determines which level of service is available to the end-user?
DSL is a distance-sensitive telecommunications service: increased distance from the central office (CO) means decreased speeds. The closer one is to the CO, the more bandwidth that can be provided.

Is DSL better than ISDN?
DSL is MUCH better than ISDN for several reasons:

• Speed - up to 4 times faster 
• Dedicated connection - no more dial-up configurations 
• Ease of installation - no more SPIDs or complex configurations 
• No usage charges - pay the same flat rate every month 
• Affordability and just one bill - the end-user receives only one bill every month for both Internet access and DSL, that is usually lower than ISDN
  

What is IDSL?
The "I" in ISDL stands for ISDN. This is for those customers of yours that may already have ISDN service. The IDSL level of service would be used for those that have the ISDN circuit in place and want to convert over to using DSL. Using IDSL is the easiest way to do so.

Are there any per-minute or usage charges associated with DSL?
No. DSL is a dedicated network service that costs the same regardless how often it is used or how much data is transferred. This predictability is one of xDSL's most attractive features. 

Does DSL have any security issues like cable modems?
No. DSL is not a shared network service like cable modems, which means that one end-user can not see what's on a neighbor's computer using DSL. The service is a private dedicated connection from the end-user to the network.

Will DSL interrupt existing phone service?
No. DSL works on its own phone line. An end user will never experience slower performance when making phone calls.

Can I use a telephone or fax machine on my DSL line?
No. DSL uses a digital technology (DSL) that is not yet compatible with telephones and fax machines.

Can the Internet keep up with so much speed?
The Internet infrastructure is constantly being upgraded to handle the rapidly increasing use of the Internet. Many servers operate at 56 Kpbs. In addition, the Internet backbone has grown in an unplanned fashion and a connection may see 20 or more routers, creating significant delay, and for TCP connections, bandwidth throttling. However, a great deal of work is underway to:

(1) increase server access speeds

(2) improve backbone and NAP bandwidth

(3) increase router speeds

(4) introduce ATM into the backbone for much lower latency. 

Furthermore, many Internet service providers will implement proxy or cache servers for frequently visited web pages, creating local access at least for these pages. At the very least, xDSL will make many Internet experiences far much better than voice band modems and the resulting market pressures will inevitably lead to capacity increases.

How does xDSL compare to cable modems?
xDSL provides a dedicated service over a single telephone line; cable modems offer a dedicated service over a shared media. While cable modems have greater downstream bandwidth capabilities (up to 30 Mbps), that bandwidth is shared among all users on a line, and will therefore vary, perhaps dramatically, as more users in a neighborhood get online at the same time. Cable modem upstream traffic will in many cases be slower than xDSL, either because the particular cable modem is inherently slower, or because of rate reductions caused by contention for upstream bandwidth slots. The big difference between xDSL and cable modems, however, is the number of lines available to each. There are no more than 12 million homes passed today that can support two-way cable modem transmissions, and while the figure also grows steadily, it will not catch up with telephone lines for many years. Additionally, many of the older cable networks are not capable of offering a return channel; consequently, such networks will need significant upgrading before they can offer high bandwidth services.

Is DSL compatible with a Macintosh?
Yes, as long as the end user has an Ethernet 10BaseT (not coax) interface and TCP/IP software (either MacTCP or OpenTransport, which is included in MacOS 7.x and later). Anybody who has been using a Mac for a dialup Internet account has TCP/IP software. TCP/IP has been a standard part of the system software. TCP/IP software is also available as an add-on for those end users that do not already have it.

What is the controversy between CAP and DMT line codes?
CAP and DMT are two "line codes" or modulation systems currently on the market today for xDSL. The Forum has taken no position on the merits or demerits of either. Each line code has its own case to make. All major xDSL vendors belong to the ADSL Forum and set aside their differences while working together to create system guidelines and market positions. As such, it can be fairly represented that the line code issue will have little bearing on the size, speed, or character of the xDSL market as a whole.

What does xDSL offer the Internet service provider?
Today, high speed Internet access is seen by many as the first "killer" application of xDSL - there is a pent up demand for higher access speeds and only xDSL can practically provide these speeds. Today's analog modems routinely offer 28.8 Kbps or 33.6 Kbps and, in a few but growing number of instances, up to 56kbps. However, 56 Kbps is probably the practical limit for analog modems. ISDN can increase this to 128 Kbps but this is still slow compared to xDSL speeds of up to 2 Mbps. xDSL will open a whole new world of virtually instantaneous downloading of massive graphics and even video applications over the Internet.